Optical structures in directional free-space optical communication systems for portable electronic devices

Abstract

A directional free-space optical communication system includes a source device including a laser diode and an endpoint device including a photodiode. The endpoint device also includes an optical structure, such as an optical adapter, that increases both angular and spatial offset tolerance between the two source device and the endpoint device.

What is claimed is: 
     
       1. An electronic device for free-space optical communication comprising:
 a first substrate comprising a circuit; 
 a photosensitive element coupled to the first substrate and to the circuit; 
 a second substrate defined by a body having a thickness, the body defining a first face and a second face opposite the first face, the second substrate:
 positioned above, and parallel to, the first substrate; and 
 extending along at least a portion of a length of the first substrate, the second substrate comprising:
 a convex protrusion proud of the first face; and 
 a tapering protrusion aligned with an optical axis of the convex protrusion, the tapering protrusion proud of the second face and tapering toward the photosensitive element at an angle facilitating total internal reflection such that light incident to the convex protrusion is focused into the tapering protrusion, reflected from a sidewall of the tapering protrusion, and is received at the photosensitive element. 
 
 
 
     
     
       2. The electronic device of  claim 1 , wherein the thickness of the body is greater than a distance from the second planar face from which the tapering protrusion extends. 
     
     
       3. The electronic device of  claim 1 , wherein the first face is a first planar face and the second face is a second planar face. 
     
     
       4. The electronic device of  claim 3 , wherein the first planar face is parallel to the second planar face. 
     
     
       5. The electronic device of  claim 1 , wherein the photosensitive element comprises a photosensitive area having a radius of less than 50 um. 
     
     
       6. The electronic device of  claim 5 , wherein the photosensitive area has a diameter of less than 50 um. 
     
     
       7. The electronic device of  claim 1 , wherein the circuit comprises an amplifier conductively coupled to an output of the photosensitive element. 
     
     
       8. The electronic device of  claim 1 , wherein the body is formed from an optically transparent material. 
     
     
       9. The electronic device of  claim 1 , wherein the body is formed from one of glass or plastic. 
     
     
       10. The electronic device of  claim 1 , wherein the convex protrusion and the tapering protrusion are integrally formed with the body. 
     
     
       11. The electronic device of  claim 1 , wherein a first diameter of the convex protrusion is greater than a second diameter of the tapering protrusion. 
     
     
       12. The electronic device of  claim 1 , wherein the tapering protrusion tapers linearly from the second surface to the photosensitive element. 
     
     
       13. The electronic device of  claim 1 , wherein the tapering protrusion tapers in a curved manner from the second surface to the photosensitive element. 
     
     
       14. The electronic device of  claim 1 , comprising a reflective material disposed over an outer surface of the tapering protrusion. 
     
     
       15. An electronic device for free-space optical communication comprising:
 a first substrate comprising a circuit; 
 a photosensitive element coupled to the first substrate and to the circuit; 
 an encapsulation material disposed over the photosensitive element and defining a tapering cavity; and 
 a second substrate defined by a body having a thickness, the body defining a first face and a second face opposite the first face, the second substrate:
 positioned above the first substrate; and 
 extending along at least a portion of a length of the first substrate, the second substrate comprising:
 a first convex protrusion proud of the first face; and 
 a second convex protrusion aligned with an optical axis of the first convex protrusion, the second convex protrusion proud of the second face such that light incident to the convex protrusion is focused toward the second convex protrusion, which in turn focuses the light into the tapering cavity so as to be received at the photosensitive element. 
 
 
 
     
     
       16. The electronic device of  claim 15 , wherein the thickness of the body is greater than a height of both the first convex protrusion or the second convex protrusion. 
     
     
       17. The electronic device of  claim 15 , further comprising a reflective coating disposed on a sidewall of the tapered cavity. 
     
     
       18. The electronic device of  claim 15 , wherein the reflective coating comprises a metallic material. 
     
     
       19. An electronic device for free-space optical communication comprising:
 a first substrate comprising a circuit; 
 a photosensitive element coupled to the first substrate and to the circuit; 
 an optical adapter positioned over the photosensitive element having a trapezoidal profile tapering toward the photosensitive element; and 
 a second substrate defined by a body having a thickness, the body defining a first face and a second face opposite the first face, the second substrate:
 positioned above the first substrate; and 
 extending along at least a portion of a length of the first substrate, the second substrate comprising:
 a first convex protrusion proud of the first face; and 
 a second convex protrusion aligned with an optical axis of the first convex protrusion, the second convex protrusion proud of the second face such that light incident to the convex protrusion is focused toward the second convex protrusion, which in turn focuses the light into the optical adapter so as to be received at the photosensitive element. 
 
 
 
     
     
       20. The electronic device of  claim 19 , wherein the optical adapter and the second substrate are formed from a material transparent to infrared light.